Known bags formed of one or more sheet materials include pouches and gusset bags. A gusset bag, for example, has a front face, a rear face (the front face and the rear face will hereinafter be inclusively referred to as main faces), and a pair of gusseted side faces that are inwardly folding into a V-shape. A gusset bag is flat with its side faces folded in. The folded side faces are unfolded to widen the rectangular top's opening, through which contents can be inserted and removed.
Some bags are designed to be re-closable and re-openable so that the contents may not be exposed when the contents are being stored and the contents may be taken out when needed. For example, a crease is provided across the main faces near the opening, along which the upper part of the bag can be folded back, or a tab with a string is attached to the upper end of one of the main faces so that the string may be wound around a button attached to the upper end of the other face to close the opening.
For facilitating and ensuring re-opening and re-closing a bag with contents, proposals have been made. For example, JP-A-2000-72159 discloses a gusset bag formed of waterproof kraft paper and having a piece of metal (e.g., aluminum) for the closure provided near the opening of the bag along the vertical direction, and JP-A-U-49-12112 discloses a gusset bag formed of paper, plastics, etc. and having a piece of metal such as a wire or ribbon provided as a closure along the opening edge of one or both of the main faces and along the side edge of the main faces.
There is also proposed side-gusseted trash bags, including a garbage bag having a thin metal ribbon or wire provided along the opening edge of each side face (see, for example, JP-B-U-51-46372) and a waste disposable bag having a fastening member provided at the four corners thereof whereby the four corners of the bag are fastened to a supporting frame formed of wire, etc. (see, for example, JP-A-61-142123).
JP-B-U-53-16507 proposes a closable bag for an article having a flexible wire attached to the upper part thereof in an inverted V letter shape as a clamping member, with which the opening of the bag can be closed.
In manufacturing closable bags with a plastically deformable wire-like member attached near the opening edge thereof, attachment of the wire-like member is generally carried out by a method in which overlapping ends of a folded film (sheeting) are joined together by heat sealing or with an adhesive with a plastic metal member inserted therebetween (see JP-A-11-100048 and JP-A-2000-72159) and a method in which an adhesive tape having a plastic metal member stuck thereto is attached to an arbitrary position of a bag (see JP-A-11-100048).
Where a bag is to be repeatedly opened and closed to take out the contents when necessary, various proposals have been made for keeping the opening wide in defiance of the V-folds of the side faces (see, for example, JP-A-8-244795).